1) Field of the Invention
The present invention relates to a mobile object location providing device and a mobile object location providing system that provide a mobile object such as a vehicle having a routing assistance device with information including map data and surrounding information and the likes around the location where the mobile object exists.
2) Description of the Related Art
Some vehicle navigation systems make it is possible to search information about eating places (restaurants, hotels) around a location of the vehicle. Precisely, a driver inputs a request to obtain the information about eating places, that request is sent to an information center, and the information center sends back information about eating places around the location of the vehicle to the vehicle. The information received is displayed on a display of the navigation system.
However, there is a time lag between when the request is sent to the information centre and when the information is received. The vehicle may have moved to a different location during that time so that it may not be convenient to go to the eating places whose information has been received.
Japanese Patent Application Laid-Open Publication No. 2002-202135 discloses a technique to solve this problem. The idea is to send to the vehicle map information of a location at which the vehicle would be after a specific period of time, i.e., at after the time lag. The position is calculated using speed and present location of the vehicle. GPS (Global Position Satellite) location data and time data are used to calculate the positions of the vehicle.
Some of the vehicle navigation systems have an inbuilt communication function. In some others, a cellular phone is used for the communications. The cellular phone is connected to the vehicle navigation system. At present, the communication speeds of cellular phones commercially available vary with radio communication providers and radio communication systems even in a single provider. For example, the communication speed by PDC (Personal Digital Cellular) method is 9.6 kbps at minimum, while the communication speed by W-CDMA (Wideband Code Division Multiple Access) method is about 144 kbps when the speed of movement is hight. Further, even in a same communication method, the communication speeds vary with service environments (antenna positions, differences of electric field intensity owing to movement speeds) of mobile communication terminals such as cellular phones. For example, the communication speed of the W-CDMA method mentioned above is 144 kbps at high speed movement, while that at slow speed movement such as walking appears 384 kbps. Further, the time required for connection preprocesses such as dial-up process and so forth varies with connection destinations.
However, in the conventional technology disclosed in Japanese Patent Application Laid-Open Publication No. 2002-202135, when to obtain the estimated position of a vehicle, only the speed per hour of the vehicle is taken into consideration. In other words, the communication speed of radio communications is not taken into consideration so that appropriate information cannot be obtained.